1. Technical Field
The present disclosure relates to an optical switch and, more particularly, to an optical switch capable of providing connection and interruption of an optical path using a Faraday rotator.
2. Description of the Related Art
An optical switch is an optical device configured to perform operations of interrupting an optical path formed between two optical ports, which serve as input and output ports for a light beam, and switching the optical path by switching the optical port to another port. Incidentally, the optical switch may have a bidirectional switching function capable of transmission and interruption of light bi-directionally between the optical ports arranged at both ends of the optical path. The bidirectional switching function is such a function that, for example, in the case of providing two optical ports opposed to each other, while in the state where an optical path from one optical port to the other is formed, the light emitted from the other optical port can be made incident on the one optical port, which is an optical path in the opposite direction.
The optical switch having the bidirectional switching function includes a mechanical type. As the mechanical optical switch, known are, for example, the one configured to drive an optical fiber itself of one optical port using an electromagnetic actuator, the one configured to actuate a prism in to or out of an optical path between two optical ports, and the like, in order to provide connection and interruption of the optical path between the optical ports. Further, another mechanical type is the one configured to switch the optical path by changing minute angle of a mirror using the known MEMS (Micro Electro Mechanical Systems). Note that an optical switch using a prism is described in Japanese patent application laid-open publication Nos. 9-236784 and 6-51255. Further, the techniques relating to an embodiment of the present disclosure are described in Japanese patent application laid-open publications Nos. 2001-117060, 2001-242420, 2002-023103, 2002-107670, and 2003-302604.
The optical switch having a bidirectional switching function has a possibility, in the future, of being used for optical communications and the like using lights having different wavelengths between one direction from one optical port to the other and the opposite direction from the other to the one. Then, the optical switch provided in an optical communication network requires high-speed responsivity and also reliability and durability with less failure and aging deterioration.
The above described mechanical optical switch has problems relating to reliability and durability, such as failure and malfunction caused by contamination of foreign matter, aging deterioration caused by wear, or the like, since movable parts are included. As is well known, mechanical systems other than MEMS require a response time for switching of about several milliseconds, which causes a problem with high-speed responsivity. The MEMS generally requires a response time of about 0.5 milliseconds, and thus is also hardly said to have extremely high-speed responsivity.
Then, an optical switch of a magneto-optical system using a Faraday rotator can be considered. As is well known, the Faraday rotator is an optical component, in which the magnetic field produced by a permanent magnet or an electromagnet is applied to a Faraday element configured with a magneto-optical material such as Y3Fe5O12 (YIG), and the component configured to rotate the polarization plane of the light traveling in the direction of the above magnetic field. In the magneto-optical system, for example, it is possible to provide connection, interruption, and switching, of an optical path between specific optical ports by configuring an optical circulator described in Japanese patent application laid-open publication No. 2001-117060. The Faraday rotator does not have a movable part or a movable mechanism, and problems such as mechanical aging deterioration caused by failure, wear and the like do not occur in principle. The response time is about 10 to 100 milliseconds, and various optical devices using the Faraday rotators are actually provided for an optical communication use.
However, the Faraday rotator is a nonreciprocal element, and an optical switch using a Faraday rotator and having a bidirectional switching function, is not in existence.